The components of a portable computer generally include a microprocessor, a display, a floppy disk drive, and a hard disk drive. Frequently, a battery is the sole power source for the components. If the battery power becomes too low, many components cease to operate. The battery must then be recharged. By reducing the power the components draw from the battery, the time between recharging can be increased.
For example, a hard disk drive may be turned off if it has not been accessed for a certain period of time, or the display screen turned off if the display has not changed for a measured time interval. A standby mode has also been utilized which is automatically entered when selected peripheral devices have not been accessed for a preset amount of time. See, for example, U.S. Pat. No. 4,980,836.
Although each of these methods contributes to increasing the time between recharging in a portable computer system, even further power saving would be helpful to extend battery life.